The present invention relates to a metal production, particularly steel. More precisely it relates to metallurgical refining vessels, particularly steel-making converters with refining oxygen blown through the top and a bottom provided with permeable refractory elements.
Metallurgical processes are known in accordance with which a molten metal bath is subjected to pneumatic stirring or bubbling by controlled injection of a stirring fluid, usually an inert gas such as nitrogen or argon. The injection of the stirring fluid is performed through permeable refractory elements mounted in the usual refractory lining which forms the bottom of the vessel containing the bath. This is disclosed, for example, in the French patent No. 2,322,202 or U.S. Pat. No. 3,259,484.
This stirring technique for a steel-making converter with oxygen blown through the top is developed throughout the world under the commercial name "LBE process" (Lance-Brassage-Equilibre). This process tends to provide, as its name indicates, a balance between metal and slag and thus cumulate to a great extent the respective advantages of the conventional top oxygen blowing and bottom oxygen blowing refining processes.
Numerous solutions have been proposed for providing in the refractory elements sufficient selective permeability to ensure a satisfactory flow of stirring fluid and at the same time to avoid penetration of the molten metal in the reverse direction. One of these solutions is described in the published European patent application No. 21,861 and includes providing interstitial passages in a sealed refractory mass either by means of smooth-walled bodies incorporated in a monolithic refractory block, or by assembling together juxtaposed refractory plates with interposition of calibrated distance pieces therebetween.
These elements, like any refractory material, inevitably wear out in contact with the molten metal. The wear is further accelerated because of the gas blowing, which causes substantial convective movements of the liquid metal at the level of the blowing elements, and whose induced effects are also felt on the service life of the surrounding conventional refractory. Experience shows that in the case of traditional converters with oxygen blowing through the top (LD type) the bottom generally wears out less quickly than the refractory of the walls, whereas it is rather the opposite which occurs when the bottom of the converters is provided with permeable refractory elements.